1. Field of the Invention
The present invention relates to an adhesive tape for preventing an implosion of a cathode ray tube (hereinafter referred to as "CRT").
2. Description of Related Art
CRTs used in television and other equipment may implode with a minor shock due to the high vacuum inside the tubes. The CRTs can be made resistant to implosion by firmly compressing an outer portion of a CRT by a metal band. However, the metal band is in direct contact with the glass of the CRT and may damage the surface of the glass due to a difference in hardness between the metal and the glass and due to protrusions formed at the welded portions of the metal band. The damage may cause a local reduction in the strength of the CRT. Moreover, the metal band may slip on the curved surface of the CRT and will not hold the CRT at an appropriate position to obtain an effective clamping or supporting effect.
An adhesive layer, including a backing, is inserted between the metal band and the CRT to avoid the above-mentioned disadvantages derived from the direct contact of a metal band with the glass of a CRT. This adhesive tape prevents cracks forming if a metal band is placed in direct contact with the CRT glass. The adhesive tape can also hold fragments of glass and minimizing the dispersion of the fragments of glass, if the CRT glass is broken.
Conventionally, such an adhesive layer containing a backing is, for example, a double-sided adhesive tape, an epoxy prepreg (see JP-B-40-22338) and so forth. Recently, an adhesive tape containing a glass cloth as the substrate is widely used (see JP-B-63-24291).
Nevertheless, the adhesive tape containing a glass cloth has the following disadvantages; when taping is completed and the tape is cut, a special cutting tool is necessary to cut the glass filament yarns. Since the glass filament yarns are brittle, when taping is carried out and the tape is bent, the glass filament yarns may be broken or their strength reduced, resulting in difficulty in taping or forming a continuous adhesive layer on the CRT glass. The conformity of the tape to the shape of a CRT is poor due to stiffness of the glass cloth backing tape, so that the tape interfere with the clamping of the metal band. A surface treatment of the glass filament yarns is necessary to coat and maintain an adhesive on a glass cloth backing. This treatment is expensive (i.e., it requires silane coupling agents) and is complex.
Furthermore, adhesive tapes are formed by slitting a glass cloth backing with coated adhesive layers thereon in the direction of the warps. By this slitting, glass filament yarn or yarns at the sides of the slit tape are broken and protrude irregularly (edge fluffs). When the tape is wound around a CRT, the irregularly protruded broken glass filaments or edge fluff lower the aesthetic appearance. Due to light passing through the glass filament yarn wefts, the tape looks bright or white and, further, such light may even disturb the display image on the CRT. In order to avoid these defects, the sides of the tapes are painted black to keep the light from the glass filament yarn wefts. This is disadvantageous in practice.
The present invention solves the above problems of the prior art.